The present invention relates to the field of energy management systems of a vehicle, and especially a vehicle with a combustion engine and a plurality of auxiliary systems.
Auxiliary systems are used in all modern vehicles. The auxiliary systems convert or consume) energy and their primary purpose is not to propel the vehicle. Examples of auxiliary systems are coolant pumps, oil pumps, air condition systems and fans. The operation of auxiliary systems represents about 3-30% of a vehicles fuel consumption, depending of the vehicle application and the operational environment.
Today, most of the auxiliary systems found in commercial heavy vehicles are not used in an energy efficient way. The control of different auxiliary systems is usually decoupled and sub optimised, which leads to an unnecessary high fuel consumption. Further, an individual optimisation of the auxiliary systems, leads to a poorer overall performance and problems in the interface between the different systems.
US2010/0322425 discloses an example of prior art energy management system used to manage energy to be supplied to a system.
There is thus a need for an improved system to control the energy auxiliary systems in an energy efficient way. Further, it is desired that such a system is low in developing and implementation costs.
It is desirable to provide an inventive system for energy management of a vehicle, which reduces the fuel consumption of the vehicle and which is easy to implement and at which auxiliary systems easily can be connected and disconnected, without the need for changes in the system control.
The invention grounds, according to an aspect thereof, upon the idea that the energy flows of a vehicle can be controlled dependent of the momentary supply and demand of energy in the energy system. By defining simple rules of how the energy is distributed, from the energy main system and to and between the auxiliary systems, a simple and efficient energy management system can be achieved. In the inventive EMS the energy is thereby traded between the energy main system and the auxiliary systems, wherein the primary energy source, i.e. the combustion engine, is the primary source of pricing. Basically, the price will be low when the combustion engine running with a high efficiency or during braking and the price high when the combustion engine running with a low efficiency. The auxiliary systems thereby purchases energy from the combustion engine when they have an energy demand, whereby the auxiliary systems has an individual price limit above which they do not purchase any energy.
The inventive EMS controls the energy flows in the vehicle by adapting the pricing rules. In the EMS the price of the energy is variable dependent of the momentary supply of energy in a global energy system, i.e. the vehicle. Each auxiliary system in the global energy system has an individual price limit; above which the auxiliary system won't purchase any more energy. Some auxiliary systems have variable price limits depending of those auxiliary systems parameters. The auxiliary systems are represented in the EMS by activation agents, which have different behaviour depending of what kind of auxiliary system they represent. Said activation agents control the energy flows in the global energy system in the EMS the auxiliary systems are divided into two categories; energy buffers and energy converters.
The energy main system provides the energy to the vehicle. The energy main system could be the fuel tank, the combustion engine, or the combustion engine including one or more auxiliary systems such as a cooling fan and a generator or an electric machine, wherein an electric machine is able to work as a generator or a motor.
The energy auxiliary systems are defined in two sub-categories; energy buffers and energy converters. An energy buffer is any system in the vehicle that can store energy, where the most obvious one is a battery. Other possible energy buffers are the cooling water, a pressure tank or the passenger compartment. All buffers are however not able to provide energy to other auxiliary systems, but just buffer within itself to reduce the future need of energy. For example the temperature in the passenger compartment can be allowed to oscillate within a range not noticeable fir the passenger. In periods with low price of the energy the temperature can be raised above the ideal temperature, such that the later on, the temperature can slowly decrease during period with higher price on energy. An energy converter converts energy from one form to another, such as a power steering device (electric energy to kinetic energy), a generator (kinetic energy to electric energy), a heater (electric energy to heat), a cooling fan (electric energy to kinetic energy) and/or any kind of actuator (electric energy to kinetic, energy).
The minimum setting of the inventive EMS comprises an energy main system, an energy buffer and an energy converter. However, any number of sub-system be added to the EMS, which will be able to manage the energy flows within the system with the same principles independently of how many sub-systems that is added to the minimum setting. For simplicity reasons a system with the minimum requirements having an energy main system, an energy buffer and an energy converter will be explained, wherein the energy main system comprises a combustion engine and an electric generator.
The energy main system is represented in the EMS by an energy main system activation agent (ms-agent). The energy buffer is represented in the EMS by an energy buffer activation agent (b-agent) and the energy converter is represented in the EMS by an energy converter activation agent (c-agent). The activation agents activate and deactivate their respective auxiliary system and controls that their energy needs is required through the EMS and that the energy is required from the energy source with the lower pricing, i.e. the energy main system or an energy buffer.
The ins-agent sets a first price for energy provided from the energy main system, wherein the first price is dependent of energy main system specific parameters. These parameters are dependent of how the energy main system is defined, but having the combustion engine as the energy main system, the parameters could be efficiency of the combustion engine, whereby the currency would be the amount of fuel needed, having the combustion engine and a generator as the energy main system the parameter would be the combined efficiency of these two components.
The b-agent purchases energy either from the ms-agent for said first price, or from another b-agent selling from a price lower than said first price, whereby the energy buffer is provided with energy from the source with the lowest price.
The b-agent sets a second price for energy provided from the energy buffer, wherein the second price is dependent of energy buffer specific parameters. Said energy buffer specific parameters preferably comprise a mean value of the purchase price of the purchased energy it the buffer and buffer efficiency.
The c-agent purchases energy from either the ms-agent or the b-agent dependent of which of the first price and the second price that is the lowest price. Obviously if there are more energy buffers connected to the system, the c-agent also can chose to buy from these, if they provide a lower price.
The b-agent and the c-agent has an individual price limit for purchasing energy, wherein the b-agent and c-agent just purchases energy if it can find a price which is lower than the individual price limit for that b-agent and c-agent respectively.
The inventive EMS ensures that the components that have the highest need always will be supplied with energy, and that that energy is taken from the most beneficial source. That is, if the combustion engine is driven in a mode with low efficiency, a component in the need of power will be delivered its power from one of the energy buffers in the system, with the condition that the energy buffer is a state of charge such that it can sell energy for a price lower than the inefficient working combustion engine. During periods of high pricing both from the combustion engine and the energy buffers, some systems might not be provided with any energy, if their individual price limit is lower than all the energy prices in the EMS.
All information needed between the activation agents is contained in the price and in the requested energy purchase. When price increases, purchase will decrease and individual system will use the content of their buffers. The primary source of pricing is the combustion, engine; the price will be low when running at high efficiency or during a braking operation, otherwise higher.
The inventive EMS further coordinates and optimises the operation of different auxiliary systems on a global level. Due to the inventive EMS the auxiliary systems are automatically and continuously adapted to the vehicles operation cycle. Adding further auxiliary systems to the vehicle and the EMS is easily done, since the individual auxiliary systems must act in the EMS under the same conditions as the existing auxiliary systems, wherein the need for manual tuning of added auxiliary systems are minimised. The newly added auxiliary system becomes an activation agent in the EMS, wherein the development costs for adding additional auxiliary systems to the global energy system can be reduced, due to the simple connection and adaption in a generic and structured control design.
Further, due to the inventive EMS, the different auxiliary systems are coordinated and optimised globally, wherein fuel consumption of the vehicle can be reduced, since the auxiliary systems uses the energy resources in the most efficient way.
Depending on how the energy main system is defined, some b-agents and c-agents can require energy for their auxiliary system directly from the ms-agent and some never directly there from. For example if the generator is comprised in the energy main system, the energy main system can deliver electric energy, wherein a plurality of b-agents and/or c-agents can purchase energy directly from the ms-agent. However, if the generator is not comprised in the energy main system, these b-agents and c-agents must purchase the energy needed for their auxiliary systems from the c-agent representing the generator in the EMS.
In a preferred embodiment of the invention, the individual price limit at which the activation agents seize to purchase energy is fixed for the c-agent and variable for the b-agent. Hence, energy converters represented by their c-agent has a priority order which is reflected in their individual price limn, the higher price limit an energy converter has, the more important it is for the vehicle that this auxiliary system are supplied with energy. For example, the heating of the passenger compartment has a lower individual price limit than the power steering. The fix individual price limit for the energy converters secures that the prioritised functions of the vehicle always can be supplied with energy.
For the energy buffer, the individual price limit is variable and preferable dependent of the state of charge for the energy buffer, such that if the energy buffer has a high state of charge its individual price limit is decreased and if the energy buffer has a low state of charge its individual price limit is increased. The variable individual price limit for the energy buffers secures that the energy buffer always is kept in a decent state of charge, such that there always is an energy buffer in the energy system.
It is preferred the variable price limit set by the b-agent depends on a state of charge of the energy buffer and the out price set by the b-agent. By including the out price of the energy from the energy buffer in the variable purchasing price limit for the energy buffer, a constant out price increase or decrease from the energy buffer is avoided.
As previously mentioned, further energy auxiliary systems of the vehicle can be connected to the inventive EMS, wherein additional energy auxiliary systems are connected to the EMS as converters and/or buffers. Wherein all buffers do not necessary have to be able to deliver energy to other auxiliary systems, just have the capacity to store energy and using it for its own function, for example the heating for the drivers/passenger compartment, which can allow an overheating, i.e. a higher temperature than the set one, during periods with cheap energy and allow a temperature below the set one during periods with expensive energy. Obviously the over and under heating is set such that it does not conflict with the comfort of the driver and/or passengers.
In a version of the inventive EMS, the EMS communicates with a travel computer of the vehicle, such that the EMS can predict an upcoming travel route. The travel computer can be any kind of travel computer, such as a satellite-based navigation system available for the driver of the vehicle or as a black box system just available to the vehicles ECU, Even though satellite-based navigation systems are the most common navigation systems, any other kind of navigation system based on other technology are possible. By using the information of from the travel computer, the EMS can have access to data of the upcoming route; such data could be topology data. The EMS can thereby predict future energy scarcities or abundances.
In a situation when the energy EMS has predicted future energy abundance, such as a long downhill slope, the EMS can add a tax to the first price, which thereby increases. By adding said tax, less purchases of energy is made directly from the energy main system, during the period that the tax is added, wherein the auxiliary system uses energy from the energy buffers, or does not purchase energy at all. Whereby the energy consumption will sink, since the state of charge of energy buffers consequently will sink. The total energy demand from the energy main system will slowly rise, wherein when the vehicle is in the state that it has an abundance of energy, all systems will be able to purchase energy and the state of charge of the energy buffers will increase, since cheap energy is available.
During these periods of abundance of energy, the EMS can subsidize the first price, in order to encourage a loading the energy buffers. A subsidize of the energy is could also be beneficial when conditions which influence the first price to rise are predicted, whereby the energy buffers can be filled before an energy scarcity is reached.
The boundaries of the energy main system can be defined as the combustion engine, or the combustion engine and a generator or even the fuel tank. Other boundary definitions are also possible. For example, if the fuel tank is the energy main system, a first energy converter would be the combustion engine, which purchases energy from the fuel tank for a first price and purchases energy to the generator for a second price, wherein the second price is dependent of the efficiency of the combustion engine. The generator purchases energy from the combustion engine for the second price and purchases energy to other auxiliary system for a third price dependent of the efficiency of the generator. However, in a preferred embodiment, the energy main system is defined as the combustion engine together with the generator, this because the energy flow from the fuel tank to the generator does not have an branches and flows only in one direction. Hence the first price set, i.e. out from the energy main system is dependent of the total efficiency of the energy main system.
The energy main system could even be comprised of a plurality of energy sources, which delivers energy to one common price dependent of the total efficiency of the energy main system. However, the EMS is adapted to a vehicle with a combustion engine, wherein such a plurality of energy sources comprises at least one internal combustion engine, such as a diesel engine.
An obvious energy buffer is a battery or a pack of batteries, wherein a plurality of batteries and/or other energy buffers can be connected to the EMS.
Common energy converters in an EMS adapted to a vehicle is an oil pump and/or a radio and/or a heating device and/or a steering servo and/or a braking servo, other all other not mentioned energy converters of a vehicle is also suitable to connect to the inventive EMS.